You need to think in percentage and not in hard money.

How many of the people born in the first quintile of wealth in the 80s are still in the first quintile? How many people born in the last quintile are now in the first quintile?

If the answer is 20% to both, great, you have no predetermination of wealth at all. if you have 50%/10%, you have what is expected in a country with correct social mobility (Most western countries post WW2 until the 70s). If its 95%/2%, or less, you have an almost non-existant wealth mobility.